Radio receiving apparatus



F. W. DUNMORE.

RADIO RECEIVING APPARATUS.

APPLICATION FILED FEB. 4. 1921.

1,405,905, Patented Feb. 7, 1922.

N AL V w n l 1/ S 5 I N "I INVENTOR.

uurrao STATES PATENT oer-ice;

FRANCIS W. DUNMORE, OI WASEINQ'ION, DISTRICT 0 COLUMBIA.

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Specification '01 Letters Patent.

Patented Feb. '7, 1922.

Application filed l'ebrnary 4, 1981. Serlal No. 442,528.

To all whom itmag concern:

Be it known that I, FRANCIS WINKLEY DUNMonn, a citizen of the United States, residing at 1727 Columbia Road, Washington, District Columbia, have invented new and useful Improvements in Radio Receiving Apparatus, of which the following is a specification. I

The invention described and claimed herein may be'used by the Government of the United States or any of its officers or employes in prosecution of work for the United States, or by any other person in the'United States, without the payment of any royalty thereon.

A receiving tube, when directly connected across the tunin condenser of a coil aerial or direction fin er has a voltage impressed on the grid in two ways: (1) by virtue of the fact that the coil circuit with tuning condenser is in tune with the incoming wave, and (2) byvirtue of the coil acting as a capacity area, one end being at or nearer ground potential than the other, as the filament battery is connected to one end of the coil, and the small grid to the other, thus giving through the battery a relatively large capacity to earth as compared to the ver slight capacity to earth throu h the smal grid. As the coil is rotated, t e im ressed voltage in case 1 varies in amplitu e from zero to maximum, accordin to the sine law, and is the useful voltagle or receivin or direction finding work. he induced voltage in case 2 is detrimental, as its amplitude is constant regardless of the position of the coil with respect to the approaching wave, and thus it is present at the position of zero induced voltage in case 1, which distorts and obscures the working point of zero induced voltage of case 1. Enduced voltages from motors, i'nition systems, etc., come under case 2. y invention relates to a method of greatly reducing the efiects of this electrical dissymmetry or so-called antenna or capacity efiect to ground as mentioned in .case 2 above, the object being to give a quieter, sharper, and less distorted minimum, thereby improving the operation of the coil as an interference preventer and its accuracy as a direction finder.

Fig. 1 represents the receiving circuit showing the iron core cou ling coil and method of winding same. ig. 2 shows a modification in the method of windin the coil. Similar numerals refer to similar parts in the two figures. 1 is the direction finder coil or coil aerial. 2 is the tuning condenser connected across the ends of the coil. 3 is a balancing condenser or meszly compensator which may be used for b ancing what little dissymmetry in capacity to earth is not taken care of by the coupli coil. 4

is a suitable primary coil wound in one or more sections as shown and connected across the 0011 and tumng condenser. This coll with condenser 2 1s resonant well away from the working wave lengths. The coil 4 is wound on an iron core 5, consisting of iron laminations about .001 inch thick. A suit-1 able secondary coil 6 is wound in one or more sections on the core between the primary sections as shown. N o. 11, Fig. 2, is a modified method of winding this coil. 7 is a 3- electrode receiving tube. 8 is a switch whereby the iron core 5 ma be'groun'ded. 9 is a suitable amplifier an accompanying apparatus. 10 is a connection at ground or counterpoise. The core 5 serves a two-fold purtenna, a transformer having two windings,

one winding being connected to the terminals of said coil antenna, the other winding being connected to the input circuit of avacuum tube, each of said windings comprising a plurality of individual sections connected in series, the sections of the primary and secondary windings being alternately arranged.

2. The combination as set forth in claim 1 in which a condenser is also connected across the terminals of said coil antenna.

3. The combination as set forth in claim 1 in which the transformer has an iron cor suitable for radio frequencies.

4. The combination as set forth in claim 3 in which the iron core is grounded.

; 5. The combination as set forth in claim 1 in which the vacuum tube has an electron emitting cathode connected to ground.

6. The combination as set forth in claim 3 in which' the iron core is connected to an electron emitting cathode of said vacuum tu e.

7. The combination as set forth in claim 6 in which the electron emitting cathode is connected to a capacity.

8. The combination as set forth in claim 2 in which the transformer has an iron core suitable for radio frequencies.

9. The combination as set forth in claim 8 in which the iron core'is grounded.

10. The combination as set forth in claim 2 in which the vacuum tube has an electron emitting cathode connected to ground.

11. The combination as set forth in claim 8 in which the iron core is connected to an elfiron emitting cathode of said vacuum tu 12. The combination as set forth in claim 11 in which said cathode is grounded.

13. The combination as set forth in claim 1 in which the sections are arranged in axial alignment, there being an odd number of secondary sections, one terminal of the centube. 14. The combination as setforth in claim trail secondary section being connected to an electron emitting cathode of said vacuum '13, in which the other terminal of the central secondary section is connected to one terminal of the remaining secondary sections which are connected in series and which are arranged alternately on either side of the central secondary section and working from center'toward the two axial 4 rality of individual sections connected in series, the primary and secondary winding being alternately arranged in axial alignment, said coil antenna being connected to said primary winding; a tuning condenser shunting said rimary winding; said tuning condenser eing shunted by two variable capacitances connected in series, the electrical conductor connecting said two capacitances being connected to ground; said secondary winding having an odd number of sections, one terminal of the central section being connected to an electron emitting cathode of a vacuum tube, said cathode being grounded, the other terminal of the central secondary section being connected to one terminal of the remaining secondary sections which are connected in series and which are-arranged alternately on either side of the central secondary section beginning at the center and working from center toward the two axial ends, the remaining terminal of the last section being connected to the grid of the receiving vacuum tube.

FRANCIS w. DUNMORE. 

